The family of naturally occurring human histatins is a group of twelve low molecular weight, abundant in histidine, peptides found in human submandibular and parotid salivary secretions (Oppenheim et al. (1986), J. Biol. Chem. 261: 1177-1182; Oppenheim et al. (1988), J. Biol. Chem. 263: 7472-7477; Troxler et al. (1990), J. Dent. Res. 69: 2-6). The primary structure of the major family members (histatins 1, 3, and 5; 70-80% of the whole family) has shown that these proteins consist of 38, 32 and 24 amino acid residues, respectively. There is a high degree of homology among these three major histatins. Histatin 5 results from post-translational cleavage of histatin 3. Many of the smaller members of the histatin family may also, in fact, originate by post-translational proteolysis of histatins 1, 3 and 5 (Oppenheim et al. (1989), Human Saliva: Clinical Chemistry and Microbiology Vol. 1 CRC Press, Boca Raton, Fla., ed. Tenovuo, J. O.; Lal et al. (1992), Arch. Oral Biol. 37: 7-13). The genes that encode histatins 1 and 3 have been localized chromosomally (vanderSpek et al., (1989), Am. J. Hum. Genet. 45: 381-387) and sequenced (Sabatini, L. M. et al. (1989), Biochem. Biophys. Res. Comm. 160:495-502). Histatins 1 and 3 appear to be derived from separate genes.
The three major human histatins exhibit specific antimicrobial activities towards diverse oral microbiota. These histatins, at physiological concentrations, are capable of killing Candida albicans in both blastopore and mycelial forms (Pollock, J. J. et al. (1984), Infect. Immun. 44:702-707; Xu, T. et al. (1991), Infect. Immun. 59 (8): 2549-2554). Histatins are also capable of killing oral bacteria, including Streptococcus mutans (MacKay, B. J. et al. (1984), Infect. Immun. 44:695-701; Xu, T. et al. (1990), J. Dent. Res. 69: 239), Porphyromonas gingivalis (Colon et al. (1993), J. Dent. Res. 72: 322) and Actinomyces viscosus (Kalpidis et al. (1992) J. Dent. Res. 72: 305).
Infection with the yeast Candida albicans is a prevalent and, in some cases, life-threatening condition affecting otherwise healthy and immuno-compromised patients. Candidal vaginitis is estimated to affect 15 to 55% of healthy young women. Candidal infections often occur in diabetics, during pregnancy, and following medication with antibiotics, steroid hormones, or oral contraceptives. (Tapper-Jones, L. M. et al. (1981) J. Clin. Pathol. 34:706-11; Sobel, J. D. et al. (1984) Infect. Immun. 44:576-580). Oral candidiasis is an early opportunistic infection of Acquired Immune Deficiency Syndrome (AIDS) in individuals infected with human immunodeficiency virus type 1, as well as a complication of radiation and chemotherapy in cancer patients. (Yeh, C. -K. et al. (1988) J. of Acquired Immune Deficiency Syndromes 1:361-366). In addition, candidal infection of denture wearers plays a primary role in dental stomatitis, a prevalent oral problem among the elderly. (Pollock, J. J. et al. (1990) NYS Dental J. 56:36-38). Candidal infections of skin and urethra are widespread problems. In patients in intensive care and immuno-compromised patients, systemic fungal infection often leads to death, since there are few safe and effective anti-fungal pharmaceuticals for intravenous use. (Burnie, J. P. et al. (1985) British Medical Journal 290:746-748). Similarly, infections with various bacterial species can cause severe disease states and even death.
Although several anti-fungal agents (e.g., clotrimazole, miconazole, ketoconazole, and nystatin) and anti-bacterial agents (penicillin, streptomycin, tetracycline and chlorhexidine) are currently available, these agents are not completely effective, can lead to drug resistant organisms and can produce adverse side effects. Many are not appropriate for oral or systemic administration. Thus, a potent, naturally occurring anti-fungal or anti-bacterial substance would provide a significant improvement in the treatment of microbial infection.